VPN Tunnel 506 vs 515e

I upgraded from a PIX506 to a PIX515e w/vac+ and all of my software based VPN connections work execpt for the two site-to-site tunnels I had. We rechecked the pre-shared keys. How can I determine why these tunnels won't work on the 515e? They were fine on the 506. We even have the 515e at the same IOS level the 506 was. Thanks for any and all assistance.

Dwayne, please double check l2l configuration again between both firewalls , all parameters must match. Debuging is your last resort! and as you know should be use in non production hours. go over again on some config checks